[Effect of uremic plasma fractions of different molecular sizes on the filterability of red blood cells]

Behaviour of the filtration of red blood cells (rbc) passed through a filter paper was investigated. The rbc were incubated in fractions of blood plasma with different molecular mass (MM). By means of an Amicon membrane XM-50 the separation of plasma from healthy and uremic patients (children) was performed into two parts of different molecular sizes one of these was the concentrate (MM more than 50 000 = K) and the other was the ultrafiltrate (MM below 50 000 = UF). By a second step the UF was divided (Amicon membrane UM-50 into an UF1 (MM below 500) and into an UF2 (MM 500 to 50 000). In addition a hemofiltrate (MM below 5 000) was used for the incubation too. This hemofiltrate was made form pooled plasma of healthy and uremic patients, respectively. Rbc was incubated in both different fractions of plasma and hemofiltrate at a temperature of 37 degrees C and for a duration of 60 min. The pH-level and the osmolality were physiological. Under the influence of uremic UF the flexibility of rbc was clearly decreased. The UF1 had the most effect of the decrease of flexibility. Therefore the small substances which are easy dialysable play also an important role in the damage of rbc in the uremia.